Can You Pass The World’s Shortest IQ Test?
What’s your IQ? I’ll plead the fifth on that one, especially after taking the world’s shortest IQ test this morning. But I’m not alone in my failure. Only 17% of people answer all three questions correctly.
Created in 2005 by MIT professor Shane Frederick, the Cognitive Reflection Test is deceptively tough. While Professor Frederick believes the test is “easy,” he says, “Reaching the correct answer often requires the suppression of an erroneous answer that springs ‘impulsively’ to mind.” That’s why more than 80% of test takers fail to score 3 out of 3.
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Here’s the first question: “A bat and a ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?” If you replied, “10 cents,” you can join the other 4 out of 5 people who answered wrong, including me.
This is the complete test:
1. A bat and a ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?
2. If it takes five machines five minutes to make five widgets, how long would it take 100 machines to make 100 widgets?
3. In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of the lake?
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What most people guess:
1. 10 cents
2. 100 minutes
3. 24 days
The correct answers:
1. 5 cents
2. 5 minutes
3. 47 days
And here are the explanations for each answer:
1. “Say the ball costs X. Then the bat costs $1 more, so it is X + 1. So we have bat + ball = X + (X + 1) = 1.1 because together they cost $1.10. This means 2X + 1 = 1.1, then 2X = 0.1, so X = 0.05. This means the ball costs five cents and the bat costs $1.05.”
2. “If it takes five machines five minutes to make five widgets, then it takes one machine five minutes to make one widget (each machine is making a widget in five minutes). If we have 100 machines working together, then each can make a widget in five minutes. So there will be 100 widgets in five minutes.”
3. “Every day FORWARD the patch doubles in size. So every day BACKWARDS means the patch halves in size. So on day 47 the lake is half full.”
